Hey, I have a novel here that I recommend to you called "Back to My Innocent Age". The main character in the book also owns a clothing store. However, there is no Na in the female protagonist's name. However, this book will let you experience the protagonist's journey of starting a business from scratch. At the same time, there are also some descriptions of life and emotions. It may also be helpful to your girlfriend. I hope my recommendation will be helpful to you. Muah ~